1. Field of the Invention
The present invention relates to a field-of-view frame switching device, and more particularly to a device for switching the field-of-view frame of a viewfinder designed for the Advanced Photo System, which uses three picture formats.
2. Description of the Prior Art
In recent years, more and more products conforming to the Advanced Photo System (hereafter referred to as the "APS") have been introduced to the market. The APS uses three picture formats to allow an image to be taken in one of the following three different frame sizes: the wide format (hereafter referred to as the "H format") that offers an aspect ratio of 9:16, the standard format (hereafter referred to as the "C format") that has the same vertical dimension as and a shorter horizontal dimension than the H format and offers an aspect ratio of 2:3, and the panorama format (hereafter referred to as the "P format") that has the same horizontal dimension as and a shorter vertical dimension than the H format and offers an aspect ratio of 1:3.
Typically, a user's selection of a specific frame size causes the switching of the field-of-view frame of a viewfinder. Conventional field-of-view frame switching devices are disclosed, for example, in Japanese Laid-Open Patent Applications Nos. H6-273826 and H8-146493. How these conventional devices achieve the switching of the field-of-view frame is schematically illustrated in FIGS. 1A to 1C and in FIGS. 2A to 2C respectively. Of these figures, FIGS. 1A and 2A show the arrangement of the field-of-view frame for the H format, FIGS. 1B and 2B show the same for the C format, and FIGS. 1C and 2C show the same for the P format.
Either of these devices has a fixed field-of-view frame 11 (indicated by broken lines) and two L-shaped movable masks 12 and 13. The vertical dimension of the C and H formats and the horizontal dimension of the H and P formats are determined by the fixed field-of-view frame 11. In each of the figures, the hatched area represents the frame size of the selected formats (H, C, or P).
In the device shown in FIGS. 1A to 1C, the two L-shaped movable masks 12 and 13 are individually moved horizontally (i.e. translated in the directions indicated by arrows C) to determine the horizontal dimension of the C format, and they are moved vertically (i.e. translated in the directions indicated by arrows P) to determine the vertical dimension of the P format. By contrast, in the device shown in FIGS. 2A to 2C, the two L-shaped movable masks 12 and 13 are individually moved obliquely (i.e. translated in the directions indicated by arrows C or P) to determine the horizontal dimension of the C format or the vertical dimension of the P format.
However, allowing the movable masks to be moved in both horizontal and vertical directions requires not only a complicated driving mechanism but also an ample space for it. On the other hand, allowing the movable masks to be moved in oblique directions requires a simpler driving mechanism, since they need to be driven along only one axis, but requires them to be driven over a comparatively long movement stroke (see FIGS. 2B and 2C). Thus, both of these devices have been imposing various restrictions in the design of compact cameras.